Well, yeah. There's no system that will defeat rubber hose exploits.

Sure, but there's a significant subset of attackers for whom this isn't an option. For example, I live in the USA. Torturing me because the government thinks there's a 7th key I'm not being up front about isn't an option for them, at least on paper.

Have a different and much smaller bitcoin wallet that serves as a decoy...and have the keys in the 1st layer of encryption.